Megacam (PI: B. McLeod) consists of 36 (2kx4k) CCDs. Each CCD has two readouts
(notice the two different gains per CCD in the image below); i.e., a total of 72
individual fits image extensions has to be reduced for each observation. In
unbinned mode (0.08"/pixel!) each observation results in about 800 MB of
For our weak lensing observations, we typically apply a 1-2 arcmin dither
pattern resulting in at least 20 individual (~5 min) observations per target. In
the image below, 25 individual observations (i.e., 1800 fits image extensions)
have been reduced and combined into a mosaic using the GaBoDS pipeline (T. Erben
et al., astro-ph/0501144), adapted to Megacam. The boxlength is about 30 arcmin
(~11kx11k, 2x2 binning).
Here the same image is shown, with X-ray (ROSAT PSPC) contours from a (z=0.5)
galaxy cluster overlaid.
Here, we zoom in to the center of the cluster. Lots a galaxies....
Zooming in further, we find an arc (!), the distorted image of a strongly lensed
background galaxy, to the right of the central galaxy and close to the X-ray
Here higher resolution X-ray contours from Chandra are overlaid, showing
structure in the central X-ray emission (Chandra data from A. Vikhlinin).